Michigan Gov. Rick Snyder refused to halt the flow of crude oil through twin pipelines in a Great Lakes waterway as they are inspected for gaps in exterior coating, saying there was no imminent threat of a spill and the shutdown could cause a shortage of propane needed for winter heating.

An environmental group sued the federal government Thursday, contending it gives pipeline owners and operators a free pass on developing legally required plans for dealing with oil spills into lakes, rivers and other inland waterways.

The National Wildlife Federation accused the U.S. Transportation Department on Tuesday of not enforcing a federal law that requires pipeline owners and operators to establish safety response plans for worst-case oil spills in lakes, rivers and other waterways.

In the weeks after an oil rig exploded and killed 11 men in the Gulf of Mexico, worried environmental groups scoured the water for oil plumes, set up animal triage centers and stretched boom across shorelines.